It is the aim of the present study to explore 1) the structure and diversity of function of proteolytic enzymes and of other sets of homologous proteins; 2) the role of limited proteolysis in physiological events such as blood coagulation, fertilization, intracellular protein degradation and extracellular protein digestion; 3) the evolutionary relationship among homologous sets of proteins; and 4) the molecular mechanism of zymogen-enzyme conversions. The amino acid sequences of bovine coagulation factor X, carboxypeptidase B, B. subtilis neutral protease, and dogfish trypsin will be completed and the structural basis of the function and evolution of these enzymes will be examined. Proteases will be isolated from various tissues to explore their molecular detail and physiological control in the fertilization of sea urchin eggs, the coagulation of bovine blood, and in both extracellular and intracellular protein degradation. A structural basis for the thermal stability of certain neutral metalloendopeptidases will be sought. The detailed mechanism of conversion of zymogens (chymotrypsinogen, trypsinogen, factor X, procarboxypeptidase) to the corresponding enzymes will be explored.